Light source comprising a light-emitting element

ABSTRACT

The invention relates to a light source comprising a light-emitting element, which emits light in a first spectral region, and comprising a luminophore, which comes from the group of alkaline-earth orthosilicates and which absorbs a portion of the light emitted by the light source and emits light in another spectral region. According to the invention, the luminophore is an alkaline-earth orthosilicate, which is activated with bivalent europium and whose composition consists of: (2-x-y)SrOx(Ba, Ca)O(1-a-b-c-d)SiO 2 aP 2 O 5 bAl 2 O 3 cB 2 O 3 dGeO 2 :yEu 2+  and/or (2-x-y)BaOx((Sr, Ca)O(1-a-b-c-d)SiO 2 aP 2 O 5 bAl 2 O 3 cB 2 O 3 dGeO 2 :yEu 2+ . The desired color (color temperature) can be easily adjusted by using a luminophore of the aforementioned type. The light source can contain an additional luminophore selected from the group of alkaline-earth aluminates, activated with bivalent europium and/or manganese, and/or can contain an additional red-emitting luminophore selected from the group Y(V, P, Si)O 4 :Eu or can contain alkaline-earth magnesium disilicate.

TECHNICAL REALM

The invention relates to a light source with a light-emitting elementthat emits in a first spectral realm, preferably in the blue and/orultraviolet range of that visual spectrum, and with a luminophore thateither is derived from the group of alkaline-earth ortho-silicates orthat contains at least a component from this group of luminescentmaterials that absorbs a portion of the emission from the light-emittingelement and then emits in another region of the spectrum, preferably inthe yellow-green, yellow, or orange ranges. The luminophore selected mayalso be used in mixtures with other luminophores from this group and/orwith other luminescent materials that do not belong to this group.

The light-emitting element is preferably an inorganic light-emittingdiode (LED), but may also be an organic LED, a laser diode, andinorganic thick-layer electro-luminescence film, or an inorganicthin-layer electro-luminescence component.

STATE OF THE ART

Inorganic LED's distinguish themselves by, among other things, longservice life, low space requirements, insensitivity to vibration, andnarrow-band spectral emissions.

Numerous emission colors, especially wide-band spectral colors, cannotbe realized from LED's because of the intrinsic emission of an activesemiconductor material, or can only be inefficiently realized. Thisespecially applies to the creation of white light.

In accordance with the state of the art, emission colors that cannot beintrinsically realized by a semiconductor are created using colorconversion.

The technique of color conversion is essentially based on the principlethat at least one luminophore is positioned above the LED “die.” Itabsorbs a portion of the emission from the die, and is thus excited tophoto-luminescence. The emission or light color of the source thenresults from the mixing of the emission transmitted from the die withthe emission emitted from the luminescent material.

Either organic or inorganic systems may basically be used. Thesignificant advantage of inorganic pigments is their higher chemical,thermal, and emission stability in comparison to organic systems. Inconnection with the long service life of inorganic LED's, long-lifeinorganic luminophores ensure a high level of color stability of thelight source consisting of both light sources.

If the emitted emission from LED's emitting blue is to be converted intowhite light, luminescent materials are used that effectively absorb theblue light (450-490 nm) and convert it into predominantly yellowluminescent emission. However, there is only a limited number ofinorganic luminophores that meet these specifications. At this time,materials from the YAG class of luminescent materials are used as colorconversion pigments for blue LED's (WO 98/05078; WO 98/05078; WO98/12757). These, however, include the disadvantage that they possess ahigh degree of efficiency only at an emission maximum of less than 560nm. For this reason, only cold white light colors with colortemperatures between 6,000 K and 8,000 K, and accordingly withcomparatively reduced color reproduction (typical values for colorreproduction index Ra lie between 70 and 75), may be used with the YAGpigments in combination with blue diodes (450-490 nm). This results inseverely-limited application possibilities. On the one hand, higherdemands are imposed as a rule during application of white-light sourcesfor general illumination, and on the other, consumers in Europe andNorth America prefer warmer light colors with color temperatures between2,700 and 5,000 K.

It is further known from WO 00/33389 to use Ba₂SiO₄:Eu²⁺ among others asa luminophore to convert the light from blue LED's. The maximum of theemission from the Ba_(2 SiO) ₄:Eu²⁺ luminescent material is, however,505 nm, so that white light cannot be reliably created using such acombination.

In works by S. H. M. Poort et al.: “Optical Properties of Eu²⁺-activatedorthosilicates and orthophosphates,” Journal of Alloys and Compounds 260(1997), pp. 93-97, the characteristics of Eu-activated Ba₂SiO₄ and ofphosphates such as KBaPO₄ and KSrPO₄ are investigated. It was alsodetermined here that the emission from Ba₂SiO₄ is about 505 nm.

PUBLICATION OF THE INVENTION

The task of this invention is to alter a light source of the typementioned at the outset so that white light colors with warmer colortemperatures, especially those color locations that lie within thetolerance ellipses established by the CIE for general illumination maybe created under conditions of high luminous efficiency and a highdegree of color reproduction quality.

This task is solved by a light source based on the invention of the typementioned at the outset so that the luminophore is an alkaline-earthortho-silicate activated with bivalent Europium of the followingcomposition:

(2-x-y)SrO·x(Ba_(u),Ca_(v))O·(1-a-b-c-d)SiO₂·aP₂O₅bAl₂O₃cB₂O₃dGeO₂:yEu²⁺

where

0≦x<1.6 0.005<y<0.5x+y≦1.6

0≦a,b,c,d<0.5 u+v=1

applies;

and/or an alkaline-earth ortho-silicate of the following composition:

(2-x-y)BaO·x(Sr_(u),Ca_(v))O·(1-a-b-c-d)SiO₂·aP₂O₅bAl₂O₃cB₂O₃dGeO₂:yEu²⁺

where

0.01<x<1.6 0.005<y<0.5

0≦a,b,c,d<0.5 u+v=1 x·u≧0.4

applies, whereby preferably at least one of the values a, b, c, and d isgreater than 0.01. A portion of the Silicon may be replaced by Galliumin both formulas.

Surprisingly it has been found that white light with good colorreproduction and a high degree of luminous efficiency may be realizedthrough a combination of a blue LED with a luminophore selected from agroup of alkaline-earth ortho-silicates activated with Europium of theabove-named composition based on the invention. In contrast toluminophores based on pure Barium ortho-silicates that emit bluish-greenlight, yellow-green and yellow to orange luminescent light may becreated using Barium-Strontium-orthosilicate mixed crystals, and evencompletely orange luminescent light may be created by incorporation ofCalcium into the ortho-silicate crystal lattice, so that, by mixing thetransmitted light from the blue LED with the luminescent light from theselected luminophore, white light with good color reproduction and ahigh degree of luminous efficiency may be generated. Displacement ofemission color by means of substitution of Ba with Sr in ortho-cilicateshas previously been known only for excitation using hard UV emission(254-nm excitation) from the above-mentioned work by Poort et al. Nodescription was made of the fact that this effect surprisingly occursmore strongly under irradiation with blue light in the range of 440-475nm. Ba—Sr—Ca ortho-silicate mixed crystals and their strong emissioncapability under excitation with low-frequency UV emission or blue lightwere previously completely unknown.

The selected luminophore may also be used in mixtures with otherluminophores of this group and/or with additional luminescent materialsnot belonging to this group. The latter luminophores include, forexample, blue-emitting alkaline-earth aluminates activated usingbivalent Europium and/or Manganese, along with the red-emittingluminophores of the group Y(V,P,Si)O₄:Eu,B₁, Y₂O₂S:Eu,Bi, or :Eu²⁺,Mn²⁺alkaline-earth Magnesium di-silicates activated with Europium orManganese according to the formula

Me_((3-x-y))MgSi₂O₈:xEu, yMn,

whereby

0.005<x<0.5 0.005<y<0.5

and Me═Ba and/or Sr and/or Ca applies.

As will be shown in the following embodiment examples, the Sr componentin the mixed-crystal luminophores based on the invention must not be toosmall in order to be able to generate white light.

Surprisingly, it has further been found that the additional inclusion ofP₂O₅, Al₂O₃, and/or B₂O₃ into the crystal lattice, as well as thesubstitution of a portion of the Silicon by Germanium, may also have asignificant influence on the emission spectrum of a given luminophore,so that this may be further advantageously varied for a particularapplication. For this, smaller ions than Si(IV) cause displacement ofthe emission maximum into a lower-frequency range, while larger ionsdisplace the bulk of the emission into higher frequencies. It couldfurther be shown that it is advantageous for the crystallinity, emissioncapability, and particularly for the stability of luminophores based onthe invention if small amounts of monovalent ions such as halogenidesand/or alkali metal ions are additionally included in the luminophore.

Based on a further advantageous embodiment of the invention, the lightsource includes at least two different luminophores, whereby at leastone is an alkaline-earth ortho-silicate luminescent material. The whitetone required for a particular application may be especially accuratelyadjusted in this manner, and Ra values greater than 80 may particularlybe achieved. A further advantageous version of the invention consists ofa combination of an LED emitting in the ultra-violet range of thespectrum, e.g., in the range between 370 and 390 nm, with at least threeluminescent materials, of which at least one is an alkaline-earthortho-silicate luminescent material based on the invention.Blue-emitting alkaline-earth aluminates activated with Europium and/ormanganese and/or red-emitting luminophores from the groupY(V,P,Si)O₄:Eu,B₁, Y₂O₂S:Eu,Bi, or from the group of alkaline-earthMagnesium di-silicates activated with Europium and Manganese may be usedas additional luminescent materials in corresponding mixtures ofluminescent materials.

Several options exist for mechanical implementation of the light sourcebased on the invention. Based on one embodiment example, it is intendedthat one or more LED chips be positioned on a circuit board within areflector, and the luminophore be dispersed in a light disk positionedabove the reflector.

It is also possible to position one or more LED chips on a circuit boardwithin the reflector, and to mount the luminophore on the reflector.

The LED chips are preferably cast in a domed shape using a transparentcasting compound. On the one hand, this casting compound providesmechanical protection, and on the other, it also improves the opticalcharacteristics (better escape of the light from the LED dice).

The luminophore may also be dispersed in a casting compound thatconnects a configuration of LED chips on a circuit board with a polymerlens, preferably one without gas content, whereby the polymers and thecasting compound include refractive indices that vary from one anotherby no more than 0.1. This casting compound may directly include the LEDdice, but it is also possible that they be cast using a transparentcasting compound (this results in a transparent casting compound and acasting compound containing the luminophore). Because of the similarrefractive indices, there is very little loss at the bordering surfacesdue to reflection.

The polymer lens preferably is of spherical or ellipsoid shape that isfilled by the casting compound, so that the LED array is secured closelyadjacent to the polymer lens. The height of the mechanical structure maythus be reduced.

In order to achieve uniform distribution of the luminophore, it isuseful if the luminophore is reduced to slurry in a preferably inorganicmatrix.

When using at least two luminophores, it is useful if the minimum twoluminophores are individually dispersed within matrices that arepositioned one after the other within the spread of light. Thus, theconcentration of luminophores may be reduced in comparison to thatobtained in a uniform dispersion of various luminophores,

The essential steps to manufacture the luminophore using an advantageousversion of the invention are shown in the following:

Depending on the selected composition for production of thealkaline-earth ortho-silicate luminophore, the stoichiometric quantitiesof alkaline-earth carbonate, Silicon dioxide, and Europium oxide outputmaterials are mixed internally, and are converted into the desiredluminophore using the solid-body reaction conventionally used in theproduction of luminescent materials in reduced atmosphere attemperatures between 1100° C. and 1400° C. For this, it is advantageousfor the crystallinity to add small amounts, preferably smaller than 0.2mol, of ammonium chloride or other halogens to the reaction mixture.Within the meaning of the displayed invention, a portion of the Siliconmay be replaced by Germanium, Boron, Aluminum, or Phosphorus, which maybe realized by the addition of corresponding amounts of compounds of thenamed elements that may be converted thermally into oxides. In a similarmanner, it is possible for small amounts of alkali metal ions to beincluded in the particular lattice.

The ortho-silicate luminophores thus obtained emit at wavelengthsbetween about 510 nm and 600 nm, and possess a half-width value of up to110 nm.

By means of proper configuration of reaction parameters and specificadditives, e.g., of monovalent halogenide and/or alkali metal ions, thedistribution of grain sizes of the luminophore based on the inventionmay be adapted to the demands of the particular application withouthaving to use damaging mechanical size-reduction processes. In thismanner, all narrow- and wide-band grain-size distributions with meangrain sizes d₅₀ of about 2 μm and 20 μm may be adjusted.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

Further advantages of the invention are explained in the following usingembodiment examples and Figures.

FIGS. 1-6 show spectra (relative intensity I dependent on wavelength) ofvarious LED light sources based on the invention; and FIGS. 7-10 showvarious embodiment examples of LED light sources based on the invention.

BEST EMBODIMENT EXAMPLES OF THE INVENTION

FIG. 1 shows the emission spectrum of a white LED with a colortemperature of 2700 K that is formed by combination of a LED emittingblue light with effective wavelength of 464 nm with luminophore based onthe invention of composition (Sr_(1.4)Ca_(0.6)SiO₄:Eu²⁺) that emitslight in a second spectral region with a maximum value of 596 nm.

Further examples for the combination of an LED emitting light at 464 nmwith one of the ortho-silicate luminophores are shown in FIGS. 2 and 3.If a yellow-emitting luminophore of composition(Sr_(1.90)Ba_(0.08)Ca_(0.02)SiO₄:Eu²⁺) is used for color conversion, awhite-light color with color temperature of 4100 K may be set, but withuse of the luminophore (Sr_(1.84)Ba_(0.16)SiO₄:Eu²⁺), for example, awhite-light color with color temperature of 6500 K may be obtained.

FIG. 4 shows the typical spectrum for the combination of a 464-nm LEDwith two ortho-silicate luminophores based on the invention. Theluminescent materials used possess the compositions(Sr_(1.4)Ca_(0.6)SiO₄:Eu²⁺) and (Sr_(1.00)Ba_(1.00)SiO₄:Eu²). For theconcrete spectrum shown in FIG. 4, a color temperature of 5088 K and acolor reproduction index Ra of 82 are obtained. However, depending onthe selected quantity ratios of luminophores, all color temperatures inthe range of about 3500 K and 7500 K may be achieved, whereby the greatadvantage of such mixtures of two ortho-silicate luminophores based onthe invention consists of the fact that Ra values greater than 80 may beachieved.

This is documented in FIG. 5 using an example. The spectrum shown standsfor the combination of a 464-nm LED with a mixture of the twoluminophores with composition of(Sr_(1.6)Ca_(0.4)Si_(0.98)Ga_(0.02)O₄:Eu²⁺) and(Sr_(1.10)Ba_(0.90)SiO₄:Eu²), which produces an Ra value of 82 at acolor temperature of 5000 K.

If a UV LED is used as an emission-emitting element that emits in afirst spectral region with a maximum of 370-390 nm, then Ra values ofgreater than 90 may be realized by means of combination of such an LEDwith a luminescent-material mixture containing the luminophores based onthe invention and shown in FIG. 4 as well as a specific portion of aBarium-Magnesium-Aluminate:Eu,Mn luminescent material. FIG. 6 shows theemission spectrum of a corresponding white-light source that produces anRa value of 91 at a color temperature of 6500 K.

Further examples may be taken from the following presentation. In it,along with the emission wavelengths of the inorganic LED's used, theresulting color temperatures, Ra values, and color locations of thelight sources are given for each composition of luminophores based onthe invention:

T=2778 K (464 nm+Sr_(1.4)Ca_(0.6)SiO₄:Eu²⁺); x=0.4619, y=0.4247, Ra=72

T=2950 K (464 nm+Sr_(1.4)Ca_(0.6)SiO₄:Eu 2+); x=0.4380, y=0.4004, Ra=73

T=3497 K (464 nm+Sr_(1.6)Ba_(0.4)SiO₄:Eu²⁺); x=0.4086, y=0.3996, Ra=74

T=4183 K (464 nm+Sr_(1.9)Ba_(0.08)Ca_(0.02)SiO₄:Eu²⁺); x=0.3762,y=0.3873, Ra=75

T=6624 K (464 nm+Sr_(1.9)Ba_(0.02)Ca_(0.08)SiO₄:Eu²⁺); x=0.3101,y=0.3306, Ra=76

T=6385 K (464 nm+Sr_(1.6)Ca_(0.4)SiO₄:Eu²⁺+Sr_(0.4)Ba_(1.6)SiO₄:Eu²⁺);x=0.3135, y=0.3397, Ra=82

T=4216 K (464 nm+Sr_(1.9)Ba_(0.08)Ca_(0.02)SiO₄:Eu²⁺); x=0.3710,y=0.3696, Ra=82

3954 K (464nm+Sr_(1.6)Ba_(0.4)SiO₄:Eu²⁺+Sr_(0.4)Ba_(1.6)SiO₄:Eu²⁺+YVO4:Eu³⁺);x=0.3756, y=0.3816, Ra=84

T=6489 K(UV-LED+Sr_(1.6)Ca_(0.4)SiO₄:Eu²⁺+Sr_(0.4)Ba_(1.6)SiO₄:Eu²⁺+BariumMagnesium aluminate:Eu 2+); x=0.3115, y=0.3390, Ra=86

T=5097 K (464nm+Sr_(1.6)Ba_(0.4)(Si_(0.9)8B_(0.02))O₄:Eu²⁺+Sr_(0.6)Ba_(1.4)SiO₄:Eu²⁺);x=0.3423, y=0.3485, Ra=82

T=5084 K(UV-LED+Sr_(1.6)Ca_(0.4)(Si_(0.99)B_(0.01))O₄:Eu²⁺+Sr_(0.6)Ba_(1.4)SiO₄:Eu²⁺+StrontiumMagnesium aluminate:Eu²⁺);x=0.3430, y=0.3531, Ra=83

 T=3369 K (464 nm+Sr_(1.4)Ca_(0.6)Si_(0.95)Ge_(0.05)O₄:Eu²⁺); x=0.4134,y=0.3959, Ra=74

T=2787 K (466 nm+Sr_(1.4)Ca_(0.6)Si_(0.98)P_(0.02)O_(4.01):Eu²⁺);x=0.4630, y=0.4280, Ra=72

T=2913 K (464 nm+Sr_(1.4)Ca_(0.6)Si_(0.98)Al_(0.02)O₄:Eu²); x=0.4425,y=0.4050, Ra=73

T=4201 K

In a preferred version of the invention, color conversion is performedas follows:

One or more LED chips 1 (see FIG. 7) are assembled on a circuit board 2.An encapsulation medium 3 in the form of a hemisphere or ahalf-ellipsoid is positioned directly above the LED's (first, to protectthe LED chip, and second, in order to be able better to decouple thelight created within the LED chip. This encapsulation medium 3 mayeither include each die individually, or it may represent a common shapefor all LED's. The circuit board 2 thus configured is inserted into areflector 4, or the reflector 4 is drawn over the LED chips 1.

A light disk 5 is placed on the reflector 4. This light disk 5 firstserves to protect the configuration, and second, the luminophore 6 ismixed into this light disk. The blue light (or the ultra-violetemission) that passes through the light disk 5 is proportionallyconverted upon passage through the luminophore 6 into a second spectralregion, so that the overall impression of white light is created. Lossesthrough waveguiding effects, which may occur in parallel plates arereduced by the opaque, scattering characteristics of the disk. Further,the reflector 4 ensures that only pre-directed light strikes the lightdisk 5 so that total reflection effects may be reduced in advance.

It is also possible to mount the luminophore 6 onto the reflector 4, asshown in FIG. 8. No light disk is required in this case.

Alternatively, a reflector 4′ may be placed over each LED chip (see FIG.9), and the reflector may be poured out in a domed shape (encapsulationmedium 31) and a light disk 5 may be positioned above each reflector 3′Or above the entire assembly.

It is useful in the manufacture of illumination sources to use LEDarrays instead of individual LED's. In a preferred version of theinvention, color conversion is performed as follows on an LED array 1′(see FIG. 10), in which the LED chips 1 area assembled directly on thecircuit board 2:

A LED array 1′ (see FIG. 10) is attached to a transparent polymer lens 7consisting of a different material (e.g., PMMA) by means of a castingcompound 3 (e.g., epoxy resin). The material of the polymer lens 7 andof the casting compound 3 are so selected that they possess refractiveindices that are as close to each other as possible, or phase-adapted.The casting compound 3 is located in a maximally hemispherical- orellipsoid-shaped hollowing of the polymer lens 7. The shape of thehollowing is significant in that the color conversion material isdispersed in the casting compound 3, and it may thus be ensured by itsshape that angle-independent emission colors are created. Alternatively,the array may first be cast with a transparent casting compound andsubsequently be attached to the polymer lens by means of the castingcompound containing the color conversion material.

In order to produce white LED's with particularly good colorreproduction n which at least two different luminophores are used, it isuseful not to disperse the two together in a matrix, but rather todisperse and mount them separately. This particularly applies tocombinations in which the final light color is created by means of amulti-step color-conversion process. That means that the emission colorwith the longest wavelength is generated in an emission process thatprogresses as follows: absorption of LED emission by the firstluminophore; emission from the first luminophore; absorption of theemission from the first luminophore by the second luminophore; andemission from the second luminophore. It is particularly preferred forsuch a process to arrange the individual materials in order in thedirection the light is spreading, since the concentration of thematerials may be reduced in comparison to a combined dispersion of theindividual materials.

This invention is not limited to the described embodiments. Theluminophores may also be included in the polymer lens (or in anotheroptical element). It is also possible to position the luminophoredirectly above the LED dice or on the surface of the transparent castingcompound, The luminophore may also be mounted in a matrix together withscattering particles. This prevents fading within the matrix and ensuresuniform light emission.

What is claimed is:
 1. A light source to create white light, including aLight-Emitting Diode (LED) to emit a blue and/or ultraviolet emission,and at least one luminophore that absorbs a portion of the blue and/orultraviolet emission and itself emits emission in another spectralregion, comprising: a luminophore, the luminophore including analkaline-earth ortho-silicate activated with bivalent Europium of one ofthe following compounds or a mixture of these compounds: a)(2-x-y)SrO·x(Ba_(u),Ca_(v))O·(1-a-b-c-d)SiO₂·aP₂O₅bAl₂O₃cB₂O₃dGeO₂:yEu²⁺ where 0≦x<1.60.005<y<0.5 x+y≦1.6 0≦a,b,c,d<0.5 u+v=1 applies; b) (2-x-y)BaO·x(Sru,Cav)O·(1-a-b-c-d)SiO₂·aP₂O₅bAl₂O₃cB₂O₃dGeO₂:yEu²⁺ where 0.01<x<1.60.005<y<0.5 0≦a,b,c,d<0.5 u+v=1 x·u≧0.4 applies; and wherein theluminophore emits emission in the yellow-green, yellow, or orangespectral regions; and wherein the color temperature and color index ofthe created white light may be adjusted by a selection of parameters inthe above-mentioned regions.
 2. The light source of claim 1, wherein atleast one of the values a, b, c, and d are greater than 0.01.
 3. Thelight source of claim 1, wherein a portion of the Silicon in theluminophore is replaced with Gallium.
 4. The light source of claim 1,further comprising an additional luminophore from the group ofalkaline-earth aluminates activated using bivalent Europium and/orManganese, and/or a second, additional red-emitting luminophore of thegroup Y(V,P,Si)O₄:Eu,Bi, Y₂O₂S:Eu,Bi, or :Eu²⁺, Mn²⁺ alkaline-earthMagnesium di-silicates with the formula Me_((3-x-y))MgSi₂O_(g):xEu, yMn,whereby 0.005<x<0.5 0.005<y<0.5 and Me═Ba and/or Sr and/or Ca applies.5. The light source of claim 1, further comprising monovalent ions,particularly halogenides and/or alkali metals, in the luminophorelattice.
 6. The light source of claim 1, wherein the LED emits in aspectral range of between 300 and 500 nm, the luminophore emits in aspectral range of between 430 and 650 nm, and the light source emitswhite light with a color reproduction index of R_(a)>70.
 7. The lightsource of claim 1, wherein one or more LED chips are arranged on acircuit board within a reflector, and the luminophore is dispersedwithin a light disk positioned above the reflector.
 8. The light sourceof claim 1, wherein one or more LED chips are arranged on a circuitboard within a reflector, and the luminophore is mounted on thereflector.
 9. The light source of claim 7, wherein the LED chips arecast together with a transparent casting compound that possesses a domedshape.
 10. The light source of claim 1, wherein the luminophore isdispersed within a casting compound that connects an arrangement of LEDchips on a circuit board preferably one without gas content, whereby thepolymer lens and the casting compound possess refractive indices thatdiffer from each other by no more than 0.1.
 11. The light source ofclaim 10, wherein the polymer lens possesses a spherical- orellipsoid-shaped recess that is filled by the casting compound, so thatthe LED arrangement is secured to the polymer lens with smallseparation.
 12. The light source of claim 1, wherein the luminophore isreduced to slurry in an inorganic matrix.
 13. The light source of claim4, further comprising a minimum of two luminophores dispersedindividually within matrices that are positioned one after the other inthe direction of light spread.
 14. The light source of claim 1, whereinthe mean grain size d₅₀ of volumetric distribution of the luminophorelies between 2 μm and 20 μm.
 15. The light source of claim 8, whereinthe LED chips are cast together with a transparent casting compound thatpossesses a domed shape.
 16. The light source of claim 12, furthercomprising a minimum of two luminophores dispersed individually withinmatrices that are positioned one after the other in the direction oflight spread.